Union Territory of Delhi, the Capital of India, is the fourth most polluted city in the world. It has 2.097 million vehicles on the road, which is more than Bombay, Calcutta and Madras put together as shown in FIG. 2 of the accompanying drawings. The vehicular population has grown over the past two decades from 1,80,424 in 1971 to 20,97,155 in 1993--an increase of 11.5 times. There has also been a spectacular growth of industry in Delhi from 40,000 units in 1978 to 89,000 units in 1992 leading to further increase in air pollution.
It may be seen from FIG. 1 of the accompanying drawings that with the increase in vehicular population, the pollution has reached alarming proportions and is the primary cause of air pollution. Ambient air quality in Delhi has been monitored by the National Environment Engineering Research Institute (NEERI) as a part of National Air Quality Monitoring Network. Sulphur dioxide, suspended particulate matter (SPM), nitrogen peroxide and carbon monoxide have been measured at different sites at Delhi. It may be seen from FIGS. 3 and 4 of the accompanying drawing that concentrations of sulphur dioxide are consistently higher at the commercial and industrial sites and has exceeded the WHO guideline range in each year since 1984. At residential sites also, it is increasing and approaching the WHO guideline. Estimated Emissions of SPM follow a pattern very similar to that for sulphur dioxide emissions. (See FIG. 5.) Emission inventories for carbon monoxide in Delhi suggest that the major source, as in most other cities of the world, is transportation and in particular motor vehicles. It is estimated by NEERI that carbon monoxide emissions have increased from 140,000 tonnes per annum in 1980 to 265,000 tonnes per annum in 1990 and total carbon monoxide emissions are projected to reach over 400,000 tonnes per annum by the year 2000. Domestic emissions were around 42,000 tonnes per annum in 1990. The increase in motor vehicle pollution accounts for the huge increase in carbon monoxide emission. Total emissions of oxides of nitrogen dioxide (NO.sub.2) in 1990 were around 73,000 tonnes per annum and follow a trend similar to that for carbon monoxide. (See FIG. 5.)
The trend in air pollution in Delhi and other big cities in India and abroad is upward through increasing urbanization and associated motorization and industrialization.